The present invention relates to a two-part type of image-forming apparatus having two units, an upper unit and a lower unit.
A so-called two-part type of image-forming apparatus has been proposed in which the body is divided into two parts, a lower unit and an upper unit supported by the lower unit and capable of opening and closing with respect thereto and which image-forming unit includes a photosensitive drum, a developing device, a charging device, an eraser device, and a cleaning device is attached to the upper unit and is replaced by an another new image-forming unit after a predetermined image-forming operation is finished.
Since the used image-forming unit is finally discarded in such an apparatus, considering economy, each component in the image-forming unit is required to provide approximately the same lifetime.
Adjustment of an amount of developer accommodated in a developing device thereof and the capacity of a used developer-collecting box of the cleaning device allows the lifetimes of these components to correspond to that of the drum. On the other hand, no outside load is applied on the eraser device and thus the lifetime thereof is longer than that of the drum.
Therefore, it is uneconomical to discard the image-forming unit including the eraser device.
Then, it can be proposed that only the eraser device is separated from the image-forming unit and the image-forming unit except for the eraser device is arranged at the upper unit.
When optical erasers such as light emitting elements are, however, used as the eraser device, the elements are required to be arranged near the drum to accomplish a predetermined eraser operation because the amount of light of each element is very low.